1. Field of the Invention
The present invention relates to the field of pumps.
2. Prior Art
For the purposes of specificity in the description of exemplary embodiments to follow, such embodiments will be described with respect to the application of the present invention to internal combustion engines, such as gasoline engines and diesel engines, though the use of the present invention is not so limited. By way of one example, intensifier type diesel engine fuel injectors are well known in the prior art, such as that shown in U.S. Pat. No. 5,460,329, the disclosure of which is incorporated herein by reference. That fuel injector is a hydraulically actuated, intensifier type fuel injector controlled by an electrically actuated double solenoid spool valve that magnetically latches by residual magnetism. However, it is to be noted that other fuel injector designs and types and other types of control valves may also be used, such as similar spool valves which do not latch, such as by way of example, single coil spring return spool valves, as are also well known in the art.
As another example, hydraulically actuated engine intake and exhaust valve systems are also known in the prior art, such as described in U.S. Patent Application Publication No. U.S. 2003/0015155A1, the disclosure of which is also incorporated herein by reference. That application discloses various embodiments of hydraulic engine valve actuation systems, subsequently referred to herein as HVA systems. The HVA systems of the foregoing application utilize a two-stage control, namely, one or more small electrically operable control valves to hydraulically control a typically larger second stage valve for controlling the flow of high pressure actuation fluid to and from the engine valve actuator. Hydraulic fluid, typically engine oil, is provided in such systems from both a low pressure rail and a high pressure rail, the low pressure rail being used by the control valve to control the position of the second stage valve, the second stage valve controlling the flow of hydraulic fluid, again typically engine oil, from a high pressure rail to the engine valve actuator in both spring return and hydraulic return engine valve actuator systems.
A typical hydraulically actuated intensifier type fuel injector, however, normally operates from a single high pressure rail, the phrase “high pressure,” of course, being relative in that the pressure typically is a high pressure for the actuating fluid for the intensifier of the fuel injector, though the fuel pressure is intensified for injection to a pressure a number of times higher than the high pressure of the actuating fluid. In the case of fuel injection, the hydraulic energy used is significant, while in HVA systems the hydraulic energy used is particularly significant. Accordingly, efficiency of the high pressure pump is an important consideration in either case, and particularly in engines using both.
Pumps generally displace a volume of fluid proportional to the angle through which their input shaft is turned. This results in a proportional relationship between the volumetric flow rate (displaced volume per unit time) from the pump and the speed at which the pump input shaft is turned. Since the load flow that the pump is replacing is usually not related to the pump input shaft angle, but varies independently with time, a time base is the most reasonable base in which to create a pump control algorithm. Therefore, this is usually what is done.